Light source for copying machine

ABSTRACT

A light source for a copying machine for reproducing an original comprising a light sensitive material having a predetermined sensibility over a given wavelength range, means for uniformly charging the light sensitive material, means for image exposing the uniformly charged light sensitive material to form a latent image thereon, and means for developing the latent image, the light source comprising a plurality of lamps where each of the lamps extends over a different wavelength range so and the intensity of each lamp is such that the response distribution over the entire visible light region is substantially flat.

United States Patent Terajima. et al.

1 1 Oct. 15,1974

[54] LIGHT SOURCE FOR COPYING MACHINE 3.644.785 2/1972 .Iaimar 355/37 X 3,682,539 8/!972 Yamai [751 lnvemors: fi g g y i ig 3.733480 5/1973 Glenn Jr. 240/31 yuzo a a, ama o; lyos 1 Hone Ebma an of Japan Primary ExaminerSamuel S. Matthews [73] Assignee: Fuji Xerox Co., Ltd., Tokyo, Japan Assistant er O'Connor Attorney, Agent. or FirmJ. T. Martin; Gerald J. [22] filed June 1973 Ferguson Jr.; Joseph J. Baker [21] Appl. No: 367,561

[57] ABSTRACT [30] Foreign Application Priority Dat A light source for a copying machine for reproducing Aug. 18 1972 Japan 47-82105 an Original comprising a light Sensitive material having a predetermined sensibility over a given wavelength [521 US. (:1 355/4, 355/37 355/70 range, means for uniformly Charging the light Sensitive 51 Int. (:1 603 15/04 material, means for image exposing the uniformly [58] Field of Search 355/4, 37, 70, 35; Charged light Sensitive material 9 form a lawmfimage 240/1 thereon, and means for developing the latent image. the light source comprising a plurality of lamps where [56] References Cited each of the lamps extends over a different wavelength UNITED STATES PATENTS range so and the intensity of each lamp is such that the response distribution over the entire visible light (1); 2/132; 33321181252: 240/31 x region is Substantially flat 3,492,070 l/l970 Zahnm .7 355/70 X 9 Claims, 4 Drawing Figures t (b) (0) 2E g E BLUE GREEN RED (nm) lnml SPECTRUM PENETRATING FACTOR PAIENTEDUCI 1 51914 SHEET 10F 2 FIG.|

Smmzm 028mm Liv FIG. 2

BLUE GREEN RED CmmEomE mWSI CIEEzmw 2.23%

mm m 0 1.! w w m SEE 023% mm w 6 U m 105E PAIENTEB 1 SW 3,841 J52 sum 2 or 2 E :3 9 an 2 5,

53 u. E Q (I) WAVE LENGTH o E 5.. s (b) 3 (c) 5 Lu 2 z E 52 :3 s E (/3 WAVE LENGTH WAVE LENGTH LIGHT SOURCE FOR COPYING MACHINE BACKGROUND or THE INVENTION 1. Field of the Invention This invention relates to improvements in the light source used in an electrophotographic copying machine of the type suited for copying colored originals.

2. Discussion of the Prior Art Generally, for copying a colored original with an electrophotograhpic copying machine, it is an essential requirement that the optical total response distribution of light be fiat over the entire visible light region. If any distortion is present in such distribution, there can be produced, in the case of copying a black-and-white original, certain portions which are reproduced and other portions which are not reproduced according to the color, that is, a phenomenon of color selection, and in the case of copying a colored original, the color balance may be destroyed to thereby deteriorate the quality of the reproductions.

The properties of the sensitive material used for copying are also extremely important in obtaining good-quality colored reproductions. That is, it is an essential requirement that such sensitive material provide a flat response distribution over the entire visible light region and respond sufficiently to any light source pres ently available. On the other hand, the light source usedin a copying machine is required to have a sufficient illuminating light intensity to equal the sensitivity of the sensitive'material and to also have light intensity that matches the light balance of the sensitive material. These requirements or conditions have an interrelation with each other, and the synthetic light source characteristics are determined from these conditions coupled with the lens and filter characteristics. The sensitive materials whichare presently used in the art can generallymeet the above-said requirements. Therefore, as the light source used with such sensitive materials, there is required one that is capable of producing a white-color light which develops a flat energy distribution and which is'as close to sunlight as possible. Such a light source must also be one that is able to make up for the inclination of the conventional sensitive material so that the peak of its response is biased toward the short wavelength side.

SUMMARY OF THE INVENTION In view of the above, the present invention, while particularly remarking the patterns of total response distribution produced from combination of the sensitive material properties, light source properties and lens and filter properties, has been devised with the object of working out a light source that satisfies every requirement for obtaining a fiat total response distribu- IIOI'I.

Other objects and advantages of this invention will become apparent upon reading the appended claims in conjunction with the following detailed description and the attached drawing.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 (a) to (c) and FIGS. 2 (a) to (d) are diagrams illustrating the principles of the present invention.

FIG. 3 is a schematic diagram of an electrophotographic copying machine having a light source according to an embodiment of the present invention.

FIGS. 4 (a) to (c) are graphical illustrations of the operation of the light source.

DESCRIPTION OF PREFERRED EMBODIMENTS If a sensitive material having properties such as shown in FIG. 7 (a) is used for copying a colored original into black-and-white reproductions, the light source suited for such a pattern of copying should (theoretically) be one whose properties together with the properties of the sensitive material provide a flat response distribution over the entire visible light region asshown in FIG. 1 (b). The properties of such a light source are as shown in FIG. 1 (c).

If a colored original is copied into colored reproductions, it needs to involve additional coloring properties if the colorant and filter properties are of a colordecomposition formula. That is, in order to obtain a total response such as shown in FIG. 2 (c) by combining the sensitive material properties shown in FIG. 2 (a) and the filter properties shown in FIG. 2 (b), there is required a light source having the properties such as shown in FIG. 2 (d). However, in both the cases of FIGS. 1 and 2, it is extremely difficult to freely change the energy of a certain specific wavelength or at a specific wavelength region with a single light source.

According to the present invention, this problem is solved by combining several groups of light source elements having respectively different properties over the visible light region to thereby produce a synthetic light source having properties close to those demanded by the sensitive material used. According to this method, no color selection takes place and colored reproductions of excellent quality can be obtained.

A preferred embodiment of the present invention is described in detail with particular reference to FIG. 3, which schematically illustrates the internal mechanism of an ordinary electrophotographic copying machine used for color reproduction having a light source assembly 2 according to the present invention shown disposed beneath a colored original 1 to be copied. The light source 2 consists of several (for example, two) illuminants 2a such as white fluorescent lamps disposed horizontally in opposed relation on the upper side and several (for example, two) illuminants 2b such as green fluorescent lamps also disposed horizontally in parallel relation to each other on the lower side, with the space between the illuminants 2b being slightly narrower than the space between the illuminants 2a as shown. The illuminants 2a and 2b can be freely adjusted in light intensity.

The copies image formed from the original by exposure to the light source 2 is projected through a reflector 3, a lens 4, another reflector 5 and a slit 6 onto the peripheral face of a drum 7 to form a latent image thereon. At the same time, the colored toner deposited on the latent image is transferred onto a copy sheet 8 supplied with rotation of the drum 7. A colored reproduction is thereby obtained.

The distribution of light energy from light source 2 can be adjusted by increasing or decreasing the number of illuminants 2a, 2b and by adjusting the intensity of light radiation therefrom. If the range of light generated by the illuminants 2a, 2b used as light source 2 covers at least three wavelength regions, for example, the short wavelength region, the middle wavelength region and the long wavelength region, shown in FIGS. 1 and 2, the light color would not be restricted to white and green as in the above embodiment.

Thus, if copying is performed with a light source having the properties as shown in FIG. 4 (b) by using a sensitive material having the properties as shown in FIG. 4 (a), the total response distribution becomes substantially flat as shown in FIG. 4 (c) and, as a result, almost perfect color reproducibility can be obtained no matter what color is present in the original.

As described above, according to the present invention, the number of illuminants designed to produce light in different regions respectively may be varied and/or the intensities of the light from the respective illuminants may be suitably adjusted to provide a light source best suited for a particular color copying operation. Thus, it is possible to obtain excellent color reproductions by using a conventional sensitive material having a readily available color sensitivity, with no fear of causing undesirable color selection. Further, since the multiple illuminants can be simple combined to produce a flat response distribution over the entire visible light region, the present .invention can be practiced with ease and at comparatively low cost. It is therefore extremely economical and high in practical utility.

Numerous modifications of the invention will become apparent to one of ordinary skill in the art upon reading the foregoing disclosure. During such a reading it will be evident that this invention provides unique light source for a copyingmachine for accomplishing the objects and advantages hereinstated.

What is claimed is:

1. [n a copying machine for reproducing an original comprising a light sensitive material having a predetermined sensitivity over a given wavelength range, means for uniformly charging said light sensitive material,

means including a light source for image exposing the uniformly charged light sensitive material to form a latent image thereon, and means for developing said latent image, said light source comprising:

a plurality of lamps where each of said lamps produces light within a different rangeof wavelengths and simultaneously illuminates said original, the

intensity of the light produced by each said lamp being such that the total response distribution of said light sensitive material to said light source is substantially uniform over the entire range of visi- 4 ble light.

2. A light source as in claim 1 where said original is black and white.

3. A light source as in claim 2 where one of said lamps is a white light source and a second is a green light source.

4. A light source as in claim 1 where said original has at least two colors.

5. A light source as in claim 1 where one of said light sources extends over a first wavelength range of the visible light region, a second of said light sources extends over a second wavelength region of the visible light region having wavelengths shorter than said first wavelength region, and a third of said light sources extends over a third wavelength region having wavelengths shorter than said second wavelength region.

6. Apparatus as in claim 1 including means for adjusting the intensity of each lamp.

7. Apparatus as in claim 1 where a first pair of said plurality of lamps are disposed in opposing relationship a first distance from said original and a second pair of said plurality of lamps are disposed in opposing relationship a second distance from said original.

8. Apparatus as in claim 7 where said first pair of lamps are closer to said original than said second pair and where said second pair of lamps are closer to one another than said first pair.

9. In a color electrophotographic copying apparatus comprising a photosensitive material having a predetermined sensitivity over a given wavelength image, means for charging the photosensitive material, means including a light source for image exposing the photosensitive material to an original and filters for color separating the original and a plurality of means for developing the latent image thus formed on the photosensitive material with different colored toners, said light source comprising a plurality of lamps where each said lamp produces light with a different range of wavelengths, means for simultaneously activating the lamps to expose the original, and means for adjusting the intensity of each lamp so that the total response distribution of the photosensitive material to the light source and the filters is substantially uniform over the entire range of visible light. 

1. In a copying machine for reproducing an original comprising a light sensitive material having a predetermined sensitivity over a given wavelength range, means for uniformly charging said light sensitive material, means including a light source for image exposing the uniformly charged light sensitive material to form a latent image thereon, and means for developing said latent image, said light source comprising: a plurality of lamps where each of said lamps produces light within a different range of wavelengths and simultaneously illuminates said original, the intensity of the light produced by each said lamp being such that the total response distribution of said light sensitive material to said light source is substantially uniform over the entire range of visible light.
 2. A light source as in claim 1 where said original is black and white.
 3. A light source as in claim 2 where one of said lamps is a white light source and a second is a green light source.
 4. A light source as in claim 1 where said original has at least two colors.
 5. A light source as in claim 1 where one of said light sources extends over a first wavelength range of the visible light region, a second of said light sources extends over a second wavelength region of the visible light region having wavelengths shorter than said first wavelength region, and a third of said light sources extends over a third wavelength region having wavelengths shorter than said second wavelength region.
 6. Apparatus as in claim 1 including means for adjusting the intensity of each lamp.
 7. Apparatus as in claim 1 where a first pair of said plurality of lamps are disposed in opposing relationship a first distance from said original and a second pair of said plurality of lamps are disposed in opposing relationship a second distance from said original.
 8. Apparatus as in claim 7 where said first pair of lamps are closer to said original than said second pair and where said second pair of lamps are closer to one another than said first pair.
 9. In a color electrophotographic copying apparatus comprising a photosensitive material having a predetermined sensitivity over a given wavelength image, means for charging the photosensitive material, means including a light source For image exposing the photosensitive material to an original and filters for color separating the original and a plurality of means for developing the latent image thus formed on the photosensitive material with different colored toners, said light source comprising a plurality of lamps where each said lamp produces light with a different range of wavelengths, means for simultaneously activating the lamps to expose the original, and means for adjusting the intensity of each lamp so that the total response distribution of the photosensitive material to the light source and the filters is substantially uniform over the entire range of visible light. 